Danny A. Riley, PhD

Professor

PhD, University of Wisconsin, Madison, WI, 1972Postdoctoral, National Institutes of Health

Graduate ProgramsProgram in Cell and Developmental BiologyProgram in Neuroscience

Research Area

The effects of actual and simulated spaceflight unloading on neuromuscular structure and function and understanding vibration injury of tissues

We are studying the cellular basis for skeletal muscle weakness, fatigue, dyscoordination, and delayed-onset soreness experienced by humans returning from spaceflight to Earth. The experimental models include both rats and humans. Adult rats have been flown 7-14 days on five NASA Space Shuttle missions and two Russian Cosmos biosatellite flights. Humans have been orbited 17 days in the Space Shuttle, and antigravity muscles were biopsied before and after flight. Long term effects are being examined by examining muscles from crew members working many months on the International Space Station. Ground-based models are also employed, including hindlimb suspension unloading of rats and for humans, one leg unloading with crutches and chronic bedrest without loading. The major findings are that muscle fibers atrophy (shrink) as expected, but atrophic muscles are more susceptible to both postflight interstitial edema (microcirculation problem) and muscle fiber tearing (eccentric contraction-like injury). Prevention of muscle deterioration during prolonged unloading will require countermeasures that deal with the multifactorial nature of the problem.

Vibration from powered tools can cause debilitating vascular and neural dysfunction in the human hand. We have developed a rat tail, vibration model for studying the injury process. Vibration damages endothelial cells, which is postulated to result in smooth muscle overgrowth and blockage of blood flow, and disrupts peripheral nerve fibers, which is likely to lead to deterioration of sensibility.